The present invention relates to an arc-extinguishing system for a contact switching apparatus.
FIG. 12 and FIG. 13 show an arc-extinguishing system for a contact switching apparatus based on the conventional technology. The contact switching apparatus comprises a movable contact 2 comprising an electrically conductive bar with contact points 1 at both ends thereof, fixed contacts 4 with contact points 3 provided opposite to the contact points 1 of the movable contact 2, a cross bar 5 for supporting the movable contact 2 and switching the contact points by conveying movement of an electromagnet device to the movable contact 2, and an arc box 6 made from heatproof resin for covering a contact switching mechanism section comprising the movable contact 2, fixed contacts 4 and the cross bar 5 to insulate electro-conducting sections of electrodes from each other.
The contact switching apparatus further comprises a plurality pieces of arc-extinguishing grid plate 7 inserted into a plurality of longitudinal concave grooves 6a formed on the internal surface of the arc box 6 and being vertical to the movable contact 2, an arc cover 10 fixed to the top surface of the arc box 6 by screws 8 and constituting a gas blow-off opening section 9 opening to an external wall section with the arc box 6, heatproof spacer pieces 11 between the arc box 6 and teeth 10a of the arc cover 10 for fixing the arc-extinguishing grid plates 7, and arc runners 12.
The arc-extinguishing system for a contact switching apparatus having the configuration described above cuts off a current between the contact points by driving arc generated between the contact points 1 and 3 of the movable contact 2 and the fixed contact 4 by means the arc-extinguishing grid plates 7 when the cross bar 5 is returned and separating the arc so as to be led into spaces between the arc-extinguishing grid plates 7 provided in parallel. In the above processes, gas generated when the arc sublimates peripheral parts with its thermal energy passes through the spaces between the arc-extinguishing grid plates 7 to the space above the arc-extinguishing grid plates 7, and further proceeds along the arc cover 10, and then is discharged from the gas blow-off opening section 9 to the outside.
The gas having passed through the spaces between the arc-extinguishing grid plates 7 is cooled down by hitting the arc cover 10 with a radiating surface widely provided on the outside thereof and going on through a space comparatively far from the place where the arc is generated, and the temperatures in the gas is left, ideally, to decrease as far as a temperature which does not give any damage to the outside, and then the gas is discharged.
Also, when the cross bar 5 closes or opens a contact according to the suction force of an electro-magnet, severe shock vibrates the arc-extinguishing grid plates 7. For this reason, the arc-extinguishing grid plates 7 inserted in the longitudinal concave grooves 6a are fixed through the spacer pieces 11 to prevent occurrence of rattling other than a switching sound as well as abrasion due to the vibration. The arc cover 10 covers the upper section of the arc box 6 so as to apply pressure to the arc-extinguishing grid plates 7 and is secured by the screws 8 near the arc-extinguishing grid plates 7.
When opening and closing the contact point, the cross bar 5 slides along a sleeve-shaped guide member 13 attached to the arc box 6 so as to avoid contact with the arc box 6 which is easily worn out.
In the conventional type of arc-extinguishing system for a contact switching apparatus, the arc box 6 and the arc cover 10 are formed with heatproof and thermosetting resin, so that the arc-extinguishing grid plates 7 are not melted even at an elevated temperature due to heat of arc, and on the other hand, those components have no elasticity, so that any method of fixing the arc-extinguishing grid plates 7 such as press fitting can not be employed to prevent rattling thereof.
For this reason, the arc-extinguishing grid plates 7 can not be fixed unless there are spacer pieces 11 having elasticity among the plates, or unless the arc-extinguishing grid plates 7 are bent or crimped, so that the shape of the arc-extinguishing grid plates 7 has to be complicated, which may cost quite a lot for assembly thereof.
Also, foreign matters such as chips of wires produced during works easily enter from the gas blow-off opening section 9, and if some of the matters have a size less than a space between the arc-extinguishing grid plates 7, the fine matters can enter into sections where the movable contact 2 and fixed contact 4 are provided, which causes burning of an electro-magnet due to imperfect contact or imperfect charge to be generated.
In the conventional type of arc-extinguishing system for a contact switching apparatus, gas generated by arc passes through the spaces between the arc-extinguishing grid plates 7, and is discharged from the gas blow-off opening section 9 as it is, so that gas with high temperature is discharged unless the arc-extinguishing grid plates 7 are made as large as a distance so as to enable sufficient cooling down of the gas.
To solve the problems as described above, the arc box 6 and the arc cover 10 are formed with heatproof and thermosetting resin in the conventional type of arc-extinguishing system, so that fine projections or the like can not be made in a narrow space due to the flowing characteristic as well as strength of resin at the time of molding, and for this reason the arc-extinguishing system becomes disadvantageously larger in accordance with the size of the arc-extinguishing grid plates 7.
Also, in the conventional type of arc-extinguishing system for a contact switching apparatus, discharged gas is diffused from the gas blow-off opening section 9, which causes insulation outside the adjacent arc-extinguishing systems to be reduced. Shorting between phases easily occurs in this section at the time of abnormality such that arc is not completely cut off, and grounding may occur when a distance from the arc extinguishing system to a control board is short.
In the conventional type of arc-extinguishing system for a contact switching apparatus, name plates for conveying various information are attached to a surface of the arc cover 10 as a front surface of the electromagnetic contactor, but heat is also conveyed to the arc cover 10 with heated gas, so that, when an ordinary paper name plate is used, it is easily peeled off. And for this reason, information is directly printed onto the arc cover 10 in many cases. However, printing onto the surface of a molded component made of resin is quite difficult and printed color is easily changed due to heat.
Also, in the conventional type of arc-extinguishing system for a contact switching apparatus, there are many cases where the cross bar 5 is constructed by heatproof resin and is reinforced with grass fibers like in cases of the arc box 6 and the arc cover 10. And for this reason, the cross bar 5 is poor in the sliding capability which promotes its abrasion, so that the guide member 13 has to be added to the bar.
It is an object of the present invention to obtain an arc-extinguishing system in which arc-extinguishing grid plates having a simple form which can be built with low cost by properly fixing the arc-extinguishing grid plates without using any spacer or the like, to obtain an arc-extinguishing system in which intrusion of foreign matters to the inside of the system is prevented, to obtain a compact type of arc-extinguishing system with a path in which a gas is easily cooled down before the gas is discharged to the outside for the purpose to make the arc-extinguishing grid plates smaller, to obtain an arc-extinguishing system in which diffusion of gas can be prevented without using any external shield, to obtain an arc-extinguishing system in which name plates can freely be selected by suppressing conduction of heat to an arc cover, and to obtain a low-cost arc-extinguishing system not requiring any additional component such as a guide member.
With the arc-extinguishing system for a contact switching apparatus according to the present invention, by pressing a thin-plate rib formed on an arc cover made of resin having elasticity against end surfaces of arc-extinguishing grid plates, the arc-extinguishing grid plates are fixed to the thin-plate rib, and for this reason there is provided the effects that trouble of mounting any spacer as an additional component on the plates can be saved, the way of assembly can be simpler, the number of components can be reduced, cost can be decreased, movement of arc-extinguishing grid plates can accurately be restricted, and generation of rattling due to vibrations of shocks and abrasion of sections where the arc-extinguishing grid plates are fixed can be prevented.
With the arc-extinguishing system for a contact switching apparatus according to the present invention, a plurality of projections vertically formed from the arc cover are inserted into spaces between arc-extinguishing provided in parallel to each other, so that movement of the arc-extinguishing grid plates can be restricted, and an area which allows foreign matters intruding from a gas blow-off opening section to pass through can be restricted by embedding the projections in the gaps between the arc-extinguishing grid plates, and for this reason there is provided the effect that intrusion of foreign matters can be prevented.
With the arc-extinguishing system for a contact switching apparatus according to the present invention, the projections are provided in a staggered form from the arc cover, and a void between the arc cover and a top surface of the arc-extinguishing grid plates is partitioned into spaces in a staggered arrangement, so that gas generated due to arc is prevented from direct discharging, and the gas can be sufficiently cooled down by extending a path for outflow of the gas, and for this reason there is provided the effect that the arc-extinguishing system can be minimized as a whole.
With the arc-extinguishing system for a contact switching apparatus according to the present invention, an internal surface of the thin-plate rib for fixing the arc-extinguishing grid plates is a corrugated surface, so that, when gas generated due to arc is going along the corrugated surface, eddy is generated, and the gas can sufficiently be cooled down by delaying a time until the gas is discharged, and for this reason there is provided the effect that the arc-extinguishing system can be minimized as a whole.
With the arc-extinguishing system for a contact switching apparatus according to the present invention, in the arc-extinguishing system for a contact switching apparatus having a plurality pieces of grid plate for arc extinction arranged outside the contact switching apparatus so as to be substantially vertical to a movable contact, and an arc box as well as an arc cover for covering the contact switching apparatus as well as arc-extinguishing grid plates, a bottom face of the arc cover opposite to the end surface of the arc-extinguishing grid plates is a corrugated surface, so that, when gas generated due to arc is going along the corrugated surface, eddy is generated, and the gas can sufficiently be cooled down by delaying a time until the gas is discharged, and for this reason there is provided the effect that the arc-extinguishing system can be minimized as a whole. Also, the section to which the gas is directly applied is a peak section of the corrugated surface, so that damages are hardly received and a surface area is increased, which enables a form adapted to effective heat radiation.
With the arc-extinguishing system for a contact switching apparatus according to the present invention, a gas blow-off opening section is opened at an angle, which gives a direction to a flow of gas discharged from the gas blow-off opening section, so that bad influence due to gas over the outside can be prevented before it works.
With the arc-extinguishing system for a contact switching apparatus according to the present invention, each of the gas blow-off opening sections is opened at an angle so that gas discharged from one of the gas blow-off opening sections and that discharged from the adjacent opening section are blown off in directions far off from each other, so that each gas after the discharge does not join to each other, and for this reason there is provided the effect that insulation is not reduced.
With the arc-extinguishing system for a contact switching apparatus according to the present invention, each of the gas blow-off opening sections is opened at an angle in a direction alternately upward and downward so that gas discharged from one of the gas blow-off opening sections and that discharged from the adjacent opening section are blown off in directions vertically far off from each other, so that each gas after the discharge does not join to each other, and for this reason there is provided the effect that insulation is not reduced.
With the arc-extinguishing system for a contact switching apparatus according to the present invention, a gas blow-off opening section having an L-shaped path is opened to the side face of the arc box, so that gas can be sufficiently cooled down by extending a path and delaying a time until the gas is discharged, and for this reason there is provided the effect that the arc-extinguishing system can be minimized as a whole.
With the arc-extinguishing system for a contact switching apparatus according to the present invention, an arc cover has a double cover structure by a void for heat insulation, so that heat is hardly conveyed to the external surface of the arc cover, and for this reason there is provided the effect that a name plate can freely selected on the external surface of the arc cover.
With the arc-extinguishing system for a contact switching apparatus according to the present invention, a cylindrical guide section for slidably supporting a cross bar for the contact switching apparatus is monolithically molded to the arc cover, and for this reason there is provided the effect that any additional component avoiding a combination of components having a bad sliding capability is not required, which allows the cost to be reduced.
With the arc-extinguishing system for a contact switching apparatus according to the present invention, a gas blow-off opening section is covered by the pectinated projections and for this reason there is provided the effect that intrusion of foreign matters bigger than a space between pectinated projections can be prevented.